Automobiles are equipped with both low-beam and high-beam outputs from their headlights. The low-beam output is usually angled downward and slightly away from oncoming traffic, in order to reduce glare for oncoming vehicles on the opposite side of the road. The high-beam output is brighter and lacks the directional requirements of the low-beam output, and as such is suitable only when alone on the road. Because of the different angular requirements of the low-beam and high-beam outputs, switching between low and high beams is not as straightforward as making the headlamp brighter or dimmer.
In many cases, automobiles are typically equipped with separate headlamps for the low-beam and high-beam outputs. The low-beam and high-beam headlamps are mounted adjacent to each other on the front of vehicles, and are aimed appropriately to meet the angular requirements of the low and high beams.
Historically, most of the headlamp designs have used incandescent bulbs, which have a limited lifetime and produce a relatively large amount of heat. In recent years, use of incandescent bulbs has been giving way to use of light emitting diodes (LEDs) as the light source in many lighting and illumination applications. In comparison, LEDs have a much longer lifetime and produce much less heat than their incandescent counterparts.
Accordingly, there exists an ongoing need for LED-based headlamp designs that reduce wasted light and improve the efficiency in converting output light from the LEDs into the low-beam light and high-beam light.